This article deals with so-called "core" utilities on a GNU/Linux system, such as less, ls, and grep. The scope of this article includes -- but is not limited to -- those utilities included with the GNU coreutils package. What follows are various tips and tricks and other helpful information related to these utilities. If sections grow too detailed, please split into separate articles.

Contents

grep

grep is a command line text search utility originally written for Unix. The grep command searches files or standard input globally for lines matching a given regular expression, and prints them to the program's standard output.

The environment variable GREP_COLORS may be used to specify different colors than the defaults.

less

less is a terminal pager program used to view the contents of a text file one screen at a time. Whilst similar to other pages such as more and pg, less offers a more advanced interface and complete feature-set.[3]

Colored output through environment variables

Add the following lines to your shell configuration file, e.g. ~/.bashrc if using Bash:

lesspipe also grants less the ability of interfacing with files other than archives, serving as an alternative for the specific command associated for that file-type (such as viewing HTML via html2text).

Re-login after installing lesspipe in order to activate it, or source /etc/profile.d/lesspipe.sh.

Vim as alternative pager

Vim has a script to view the content of text files, compressed files, binaries, directories. Add the following line to your shell configuration file, e.g. ~/.bashrc for Bash:

alias less='/usr/share/vim/vim73/macros/less.sh'

ls

ls is a command to list files in Unix and Unix-like operating systems.

Colored output can be enabled with a simple alias. File ~/.bashrc should already have the following entry copied from /etc/skel/.bashrc:

alias ls='ls --color=auto'

The next step will further enhance the colored ls output; for example, broken (orphan) symlinks will start showing in a red hue. Add the following to ~/.bashrc and relogin, or source the file:

eval $(dircolors -b)

rm

rm is a command to delete files and directories.
It could be very dangerous so it is prudent to limit its scope:

alias rm=' timeout 3 rm -Iv'

This alias suspends rm after three seconds, asks confirmation to delete three or more files, lists the operations in progress and does not store itself in the shell history file if the shell is configured to ignore space starting commands.